<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <!-- 引入vue -->
  <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
  <div id="root">
    姓： <input type="text" v-model:value="firstName"><br />
    名： <input type="text" v-model="lastName"><br />
    姓名：<span>{{firstName}}-{{lastName.slice(0,3)}}</span>
  </div>
  <script type="text/javascript">
    Vue.config.productionTip = false //阻止 vue 在启动时生成生产提示。、
    new Vue({
      el: '#root',
      data: {
        firstName: '张',
        lastName: '三'
      }
    })
  </script>
</body>

</html>